Method and apparatus for starting and operating gaseous electric discharge devices



y 1935- L. J. BUTTOLPH 2,001,518

METHOD AND APPARATUS FOR STARTING AND QPERATING GASEOUS ELECTRIC DISCHARGE DEVICES Filed July 26, 1932 2 Sheets-Sheet 1 INVENTOR TTORNEY May 14, 1935. J BUTTOLPH 2,001,518

METHOD AND APPARATUS FOR STARTING AND OPERATING GASEOUS ELECTRIC DISCHARGE DEVICES Filed July 26, 1932 2 Sheets-Sheet 2 Patented May 14, 1935 v UNITED STATES METHOD AND APPARATUS FOR STARTING AND OPERATING GASEOUS ELECTRIC DISCHARGE DEVICES Leroy J. Buttolph, Grantwood, N. J., assignor to General Electric Vapor Lamp Company, Hoboken, N. J a. corporation of New Jersey Application July 26, 1932, Serial No. 624,838

Claims.

The present invention relates to electric gaseous discharge devices generally, and in particular to vapor are devices.

' A particular object of the invention is to provide an artificial light source which emits light closely approximating daylight. Another object of the invention is to provide a light source of high luminous efllciency. A further object of my invention is to provide a light source having a long useful life. Another object of my invention is to provide means whereby incandescent lamps can be used as ballast for an electric gaseous discharge device. Still another object of my invention is to provide means whereby failure of one of the ballast lamps will not render the gaseous discharge device inoperative. Still other objects and advantages of my invention will appear from the following detailed specification or from an inspection of the accompanying drawings.

The invention consists in the new and novel method of operation, and in the novel combination of elements, as hereinafter set forth and claimed.

In operating arc discharges from a constant potential source the use of a ballast in series with the arc is essential, due to the well known negative volt-ampere characteristic of this type of discharge. The resistance which has ordinarily been employed to provide this ballasting action has resulted in a considerable loss of energy which might be utilized in the production of light by the use of incandescent lamps as ballast, such as has been heretofore proposed. Unfortunately, however, this substitution has proved impossible, especially where a vapor arc is being operated. It is characteristic, for example, of the mercury vapor are that at the instant of starting it draws over twice the normal current. Moreover, in alternating current devices of the rectifying or Cooper Hewitt type there is a possibility during the starting period of transient arcing between the anodes, due to the condensation of mercury vapor on these anodes. In either case the incandescent lamps, if connected as ballast during this period, are subjected to an extreme overload which results in their rapid destruction. Moreover the incandescent lamps allow a high current surge at the moment the arc is started. This is due to the fact that the cold resistance of the tungsten filament lamps commonly used is so low (being but a twelfth of the normal operating resistance thereof) that the initial current surge in the mercury arc is unduly accentuated. This combination of incandescent lamps with a mercury vapor arc is extremely desirable, however, since the combined light of these units has been found to closely approximate daylight. I have now discovered a novel combination of elements cooperating in a novel manner,- as described hereinafter, which permits the use of incandescent lamps as ballast for gaseous discharge devices despite these initial variations in arc currer. without in any way impairing the life of the incandescent lamps. According to my novel invention the arc discharge is initiated with the usual ballast resistance in series with the discharge, and the incandescent lamps are preheated by operation on normal voltage during the starting period. Then after the arc current has decreased to substantially the normal value the incandescent lamps are substituted for the resistance. Due to the preheating of these lamps this transition is relatively smooth. The operation of the incandescent lamps at normal voltage during this starting period is also desirable because of the fact that the desired light quality is thereby attained from the moment the combined unit is switched on. As a further novel feature I provide means whereby this substitution of the incandescent lamps for the ballast resistance is avoided if the incandescent lamps are impaired, thus avoiding unnecessary shut downs of the gaseous discharge device. I have also discovered a novel means by which the delay period can be easily determined by the arc current itself, thus providing means whereby the starting period may be made the absolute minimum which is consistent with proper operation of the incandescent lamps.

For the purpose of illustrating my invention I have shown several embodiments thereof in the accompanying drawings, in which Fig. 1 is a schematic diagram of the connections of an alternating current mercury arc lamp operating with incandescent lamp ballast,

Fig. 2 is a schematic diagram of a modification of the circuit of Fig. 1,

Fig. 3 is a schematic diagram of another modification of the circuit of Fig. 1, and

Fig. 4 is an elevational view of the relay used in the circuit of Fig. 3.

In these drawings, with special reference to Fig. 1 there is shown a mercury vapor arc lamp 1 of the Cooper Hewitt type, having a mercury cathode 2, starting band 3 and anodes l. Said cathode 2 is connected through an inductance 5 to an intermediate point on the autotransformer 6. One of the anodes l is connected directly to one end of said autotransformer, while the other anode 4 is connected to the other end of said 2 autotransformer 8 through a heater unit I, ,a ballast resistance 8, the magnet coil 8, and in. candescent lamps III. A- single pole, double throw, mercury switch is mounted on a pivoted magnetic support I: which is within the field of the inductance 5. The middle terminal of said switch is connected to a point between the ballast resistance 8 and the magnet c0118, while the terminal at, the end of said switch which is normally down is connected to a tap on said autotransformer which is 64 volts (where the lamps I8 are 32 volt lamps) away from the end of said autotransformer to which said lamps are connected. The remaining terminal of said switch is connect-. ed directly to the same anode 4 with which the ballast is in series. As disclosed in Patent 1,990,-

1 152, grantedFeb. 5, 1935 to Wilford J. Winninghoii, where the ballast is all inserted in a single anode lead the voltage applied between the anodes and the cathode should be asymmetrical in order to balance the arc current during successive half cycles. In the present case, with a standard mercury arc lamp having an arc tube an inch in diameter and fifty inches long, excellent results are obtained by connecting the inductance 5 to a tap which is volts away from the lead to the direct connected anode and 194 volts away from the other end of said autotransformer. The support I2 is normally locked against pivotal movement bothby the bell crank I8, and by a dog I4. Said dog I4 is adapted to be moved out of the locking position by the magnet coil 8, while the bell crank I3 is moved out of the locking position, after a predetermined delay, by means of a bimetallic element I5 which is in thermal relation to the heating unit I. Where additional incandescent lamps are desired, in order to increasethe red component of the light, lamps I6 are provided, these lamps preferably being of a low voltage type, say 32 volts, and connected to suitable taps on the autotransformer 8, in order to gain the greater luminous efficiency of these low voltage lamps. A mercury switch I], of the type commonly called a shifter, is located in operable relation to the inductance 5 and has one terminal thereof connected to a point between said inductance and the cathode 2. The other terminal of said shifter is connected to the starting band-8 and also through a resistance I8 to an anode 4.

In the use and operation of this novel apparatus, upon application of a suitable potential to the autotransformer 8 current immediately flows through the lamps I6, and also from one end of said autotransformer through the lamps III, magnet coil 8 and switch II back to a tap on said autotransformer. At the same time current flows from, the same tap through said switch II, ballast resistance 8, heating unit I, resistance I8, shifter l1, and inductance 5 back to said autotransformer. This current energizes the inductance 5 which thereupon causes said shifter to open the circuit, interrupting the current flow through said inductance, with the result that a voltage surge is generated within said inductance which initiates the arc through the lamp I in a well known manner. on one half cycle this are current flows directly from one end of the autotransformer 8 to an anode 4, while on the other half cycle the current flows to the other anode 4 from the previously mentioned tap on said autotransformer through the switch II, ballast resistance 8, and heating unit 1. These halfwave currents then combine in a full wave arc to the cathode 2, returning to the autotransformer through the inductance 5. Said inductance tends aooisic to move the support H as soon as it is energized, but said support is locked againstmovement by the bell crank I8 until the discharge current has been flowing through-the heating unit I for an interval of say 45 seconds. During this interval the bimetallic element I5 gradually warps, forcing thebell crank out of the locking position, and at the same time the lamp I heats up and the current therethrough approaches normal. During this starting period the lamps III are, of course, operated continuously at normal voltage, while the lamp I is operated with a potential of 90 volts on the unballasted half cycle and .130 volts on the ballasted half cycle. Since the dog I4 is continuously held out of the locking position by the magnet coil 8 so long as current flows through the lamps III, the support I2 is released as soon as the bell crank I3 is moved out of the locking position. Said support is thereupon immediately moved by the inductance 5 to change the circuits through the switch II. As shown, said switch II is preferablycurved in order" to disconnect one end terminal thereof before the other end terminal is connected. This is desirable although not essential, it being obvious that with this construction both the lamps III and the ballast resistance 8 will be connected in series with the arc during the transitional stage, whereas if all three terminals of the switch are connected together during the transition all of the ballast will be momentarily short circuited. In any case as the switch II again comes to rest a new circuit is established from the end of the autotransformer 6 through the preheated lamps I0, magnet coil 8 and switch II directly to an anode 4, it being obvious that the ballast resistance 8 and heater unit I are now short circuited by the switch II. Thus the lamp I continues to operate with the incandescent lamps as ballast, with a potential of 194 volts applied during the ballasted half cycle. Said lamps I0 have a greater resistance than the ballast resistance 8, however, and hence the lamp I continues to operate with substantially the same current on each half cycle.

In case one of the lamps I0 burns out, or is otherwise destroyed, the arc in the lamp I will be extinguished, whereupon the switch II will be moved back to its starting position. The mercury arc will then be reinitiated as before, and the bell crank I3 will be gradually moved out of the locking position. The magnet coil 9 will be deenergized, however, in this case so that the dog I4 will remain in the locking position until the faulty lamp I8 is replaced. In the meantime the arc will continue to operate with the ballast resistance 8 connected in series therewith, only the incandescent lamps I8 being inoperative.

With the circuit of Fig. 1 failure of either of the ballast lamps I8 causes both to be rendered inoperative. Where this is undesirable, as in locations that are not frequently serviced, the ballast may be divided and half placed in each anode lead in the conventional manner, as shown in Fig. 2. In this case the cathode 2 is connected through the inductance 5 to the midpointof the autotransformer 6, while each of theanodes 4 is connected in a symmetrical manner through a ballast resistance 8, Heater unit I, magnet coil 8, and a lamp I 0 to an end of said autotransformer. Two mercury switches II are provided, each being mounted on a separated pivoted support I2. The midpoint of each switch is connected to a point between a magnetic coil 9 and a heater unit -l, while the terminal at the end of each switch which is normally downv is connected to a tap 32 volts away from the end of the autotransformer. The other, terminal of each switch is directly connected to the associated anode 4. Each support I2 is independently locked against movement by the inductance 5 in the same manner as in Fig. 1. The shifter I1 is likewise connected in the same manner as in Fig, 1, as are also the lamps IS.

The operation of the apparatus shown in this figure is quite similar to that previously described. Upon application of potential to the autotransformer 6 the lamps I0 and I6 are immediately lighted, and the arc is initiated in the usual manner in the mercury arc lamp I. At the start the are is operated with the two resistances 8 as ballast, while the lamps I0 are operated on their normal potential. After an interval the supports I2 are released as previously described,'whereupon the lamps III are included in the respective anode circuits as ballast, and the resistances 8 are short circuited. In case either lamp IIl burns out the arc is extinguished. The switches II thereupon return immediately to their starting position and the arc is reinitiated in the usual manner. After the desired interval the good lamp III is inserted in its anode lead as ballast in the previously described manner. The other support I2 continues to be locked by the dog I4 in its normal starting position, however, due to the fact that the circuit through the associated magnet coil 9 is interrupted by the break in the lamp III. Hence the ballast resistance 8 is left in this anode lead. until the defective lamp I0 is replaced, and the arc operates with resistance ballast on one half cycle and lamp ballast on the other half cycle. Thus failure of any incandescent lamp does not affect in the slightest either the continued operation of the mercury are or of any of the other incandescent lamps.

The circuit shown in Fig. 3 is similar to that of Fig. 1, except for the operating mechanism of the switch I I. In order to make the operation of this switch directly responsive to the current flowing in the mercury arc the relay mechanism shown in detail in Fig. 4 is incorporated in this circuit. As shown in these figures the armature I9 is pivotally supported by a yoke 20 in the outer fringe of the field of the inductance 5. The switch I I is mounted on a heavy pivoted support 2| which is likewise carried by the yoke 20. A series of leaf springs 22 are affixed to the lower side of the armature I9, the longest thereof bearing against one end of a metal strip 23 which is attached at an intermediate point thereof to the support 2 I. The other end of said strip 23 turns downwardly and is adapted to engage the turned up end of the armature I9 when said armature is abruptly moved, locking the support 2| against rotation under the influence of the force exerted by the leaf springs 22. The armature 2| is pivotally supported by the yoke 20 adjacent to the coil 9 which is likewise supported by said yoke. The lower end of said armature is in the form of a hook which is normally so positioned as to engage a suitable notch in the support 2| to prevent operation thereof by the springs 22.

In the use and operation of this apparatus, upon application of a suitable alternating current potential to the autotransformer 6 current immediately flows through the lamps I0, lamps I6 and magnet coil 9, and likewise through the circuit comprised by the resistance I8, shifter I1 and inductance 5, energizing said inductance.

The shifter I1 is thereupon rotated to the open circuit position, and the ensuing voltage surge generated within said inductance initiates the arc in the lamp I in a well known manner. This current through said inductance is limited to a rather low value, of say 0.75 ampere, by the resistance I8, and hence the armature I9, being located in the fringe of the magnetic field about said inductance, is not appreciably attracted by the shifter current. As soon as the arc is initiated, however, a current of the order of 6 amperes flows through said inductance. This large current saturates the core of said inductance and .thus increases the stray field about the armature I9, causing it to be suddenly attracted toward said inductance. As a result of this sudden movement of the armature the bent up end thereof engages the turned down end of the strip 23, looking the support 2| against movement before the springs 22 can overcome the inertia of the support 2| to move it. The armature 24 is, of course, held out of the locking position due to the lamp current flowing through the magnet coil 9. As the arc current decreases the field about the inductance 5 gradually decreases, lesseningits attraction for the armature I9, with the result that the springs 22 cause said armature to gradually recede from said inductance until eventually, after the arc current has dropped to substantially the normal Operating value, said armature releases the metal strip'23.

This unlocks the support 2 I, and allows the springs 22 to force said strip23 upwardly, moving the support 2| and switch II to the normal operating position. The lamps I 0 are thereupon included in the arc circuit, and the ballast resistance 8 short circuited in the same manner as in the circuit of Fig. 1. In order to obtain this action of the armature I9 it is essential, of course, that said armature should remain balanced and not make contact with the iron core of the inductance 5, and means such as a fiber spacer is commonly used to prevent such contact, which would freeze the armature and prevent its response to the decreasing current.

If a lamp I0 burns out the arc is extinguished, and then reinitiated in the manner previously described. The armature 24 remains in the locking position, however, and thus prevents the operation of the switch II, with the result that the arc continues to operate with the resistance 8 as ballast until the lamp I 0 is replaced.

While I have illustrated my invention by reference to specific embodiments thereof it is to be understood that it is not limited thereto, but that various changes, substitutions or omissions \vithin the scope of the appended claims may be made either in the structure or the mode of operation, without departing from the spirit thereof. It is, moreover, to be understood that the invention is applicable to the various types of gaseous discharge devices, operating with either a hot or cold cathode, or with two cathodes and a reversing discharge, whenever the initial operating characteristics of the discharge device preclude the immediate insertion of an incandescent lamp in series therewith.

I claim as my invention:-

1. In combination, an electric gaseous discharge device, a ballast resistance connected in series therewith, an incandescent lamp, means to substitute said lamp for said resistance, and means to preheat the filament of said incandescent lamp before it is connected in series with said device.

2. -In combination, an electric gaseous discharge device, a ballast resistance connected in series therewith, an incandescent lamp, means, responsive to current flow through said discharge device to Substitute said lamp for said resistance, means to prevent the immediate response of said last vice to substitute said lamp for said resistance,

means to prevent immediate response of said last mentioned means, means to preheat said incandescent lamp, and means operative upon failure of said incandescent lamp to prevent substitution of said lamp for said resistance.

5. In combination, an electric gaseous discharge device having a cathode and two anodes, an autotransformer, one or said anodes being connected to a point on said autotransformer through a ballast resistance, the other of said anodes being connected to another point on said autotransformer, a connection from said cathode to an intermediate point on said autotransformer, an incandescent lamp connected on one side to the end of said resistance which is connected to said autotransformer and on the other side to a point of higher potential on said autotransformer, means to open the connection between said resistance and said autotransformer, and means to short circuit said resistance.

6. In combination, an electric gaseous discharge device having a cathode and two anodes,-

' an autotransformer, one of said anodes being connected to a point on said autotransiormer through a ballast resistance, the other of said anodes being connected to another point on said autotransformer, a connection from said cathode to an intermediate point on said autotransiformer, an incandescent lamp connected on one side to the end of said resistance which is connected to said autotransiormer and on the other side to a point of higher potential on said autotransformer, means responsive to current flow through said discharge device to open the connection between said resistance and said autotranstormer and to short circuit said resistance, and means to prevent the immediate response of said last mentioned means.

7. In combination, an electric gaseous dis- 7 charge device, a ballast resistance and an inductance connected in series therewith, an incan descent lamp, means responsive to current flow through said discharge device to substitute said lamp for said resistance,' and meanscomprising a locking mechanism responsive to the field about said inductance to prevent operation of said last mentioned means until the current through said discharge device has decreased to a predeter-r mined value.

8. In combination, an electric gaseous discharge device, a ballast resistance and an inductance connected in series therewith, an incandescent lamp, switching means to substitute said lamp for said resistance, an armature in the field of said inductance, a yielding connection between said armature and said switching means, and means on said armature to lock said switching means against movement, the inertia of said switching means being sufiicient to prevent operation thereof by said yielding connection before said armature locks said switching means whenever a current of more than a predetermined value suddenly flows through said inductance, said yielding means then balancing said armature against the attraction oi. said inductance, the resilience of said yielding means being sufiicient to move said armature to unlock said switching means when the current through said inductance falls to a predetermined value.

' 9. In combination, an inductance, an armature in the field of said. inductance, a switching meanspa yielding connection between said armature and said switching means, and means on said armature to lock said switching means against movement, the inertia of said switching means being sufilcient to prevent operation thereof by said. yielding connection before said armature locks said switching means whenever a current of more than a predetermined value suddenly'flows through said inductance, the resilience of said yielding means being sufiicient to move said armature to unlock said switching meanswhen said current falls to a predetermined value.

10. The method of operating a gaseous discharge device which comprises starting the discharge in said device while utilizing a resistance as ballast, preheating the filament of an incandescent lamp by passing therethrough a current equal to the current flowing through said discharge device under conditions of thermal equilibrium, and then substituting said lamp for said resistance after the discharge current has reached a stable value.

LEROY J. BUTI'OIPH. 

